This disclosure relates to compositions and methods of preparation of compositions comprising transparent blends of polycarbonates and poly(ether-ester) copolymers, methods for their manufacture, and articles formed therefrom.
Polycarbonates are useful in the manufacture of articles and components for a wide range of applications, from automotive parts to electronic appliances. Because of their broad use, polycarbonates are often combined with other polymers to achieve the desired properties.
Poly(ether-ester) copolymers, sometimes referred to as thermoplastic copolyetherester (TPEE) elastomers, are a special class of elastomeric materials that can be molded using conventional molding equipment, and that exhibit the elasticity and resistance to impact and flex-fatigue of conventional cured rubbers. This combination of properties is attributable to the phase separation between the amorphous (soft) polyester units containing the polyether segments and the crystalline (hard) polyester segments. Because the immiscible segments are copolymerized into a single macromolecular backbone the necessary phase separation that occurs results in discrete domains. The amorphous soft-blocks provide the elastomeric properties of flexibility and low temperature impact, while the presence of the crystalline hard block results in discrete melting points, heat and chemical resistance, and mechanical strength. These materials are also commonly characterized by a brittleness point that is lower than those of conventional rubbers, superior resilience, low creep, and very good resistance to oils, fuels, solvents, and chemicals.
A drawback of poly(ether-ester) copolymers is their relative lack of transparency, again due to the phase separation of the segments. Blends of poly(ether-ester) copolymers with thermoplastic polymers such as polycarbonate or polyester lack transparency as well. Currently available polycarbonate-poly(ether-ester) copolymer compositions also lack room temperature impact ductility and the performance of photochromic dyes is compromised in polycarbonate-poly(ether-ester) copolymer compositions. There remains a need for polycarbonate-poly(ether-ester) copolymer compositions that are transparent, that have good room temperature impact ductility, and that maintain good photochromic dye performance. This disclosure addresses the challenge of formulating polycarbonate-poly(ether-ester) copolymer compositions to achieve the desired property balances for applications that require transparency and ductility, and in which photochromic dye performance is maximized.